Methods and systems for associating and translating virtual local area network (VLAN) tags

Abstract

Methods and systems for associating and translating VLAN tags are disclosed. In one implementation, multiple different member VLAN tags are associated with a translation VLAN tag. When a frame addressed to an unknown MAC address and containing one of the member VLAN tags is received, the frame is flooded to the translation VLAN and to ports associated with the source member VLAN other than the originating port. In the copy sent to the translation VLAN, the VLAN tag is replaced with the tag of the translation VLAN, for tagged ports. For untagged ports, the input VLAN tag may simply be stripped from the frames. When a layer 2 frame addressed to an unknown MAC address and containing the translation VLAN tag is received, the layer 2 frame is flooded to each of the member VLANs and to ports of the translation VLAN other than the originating port. The VLAN tag in the frames forwarded to each of the member VLANs may be replaced with the VLAN tag corresponding to each member VLAN, for tagged ports. For untagged ports, the input VLAN tag may simply be stripped from the frames. MAC address learning for frames received from member VLANs extends to the translation VLAN but not to other member VLANs. MAC address learning for frames from the translation VLAN extends to the member VLANs.

Description

TECHNICAL FIELD[0001]The present invention relates to methods and systems for layer 2 frame switching. More particularly, the present invention relates to methods and systems for associating and translating VLAN tags in layer 2 frame switching.BACKGROUND ART[0002]Local area networks (LANs) have been used to facilitate communications between end users connected to the same physical network. Individual LANs may be bridged to allow end users to communicate with other end users connected to different networks using layer 2 switches. Bridged LANs may be further interconnected with other bridged LANs using routers to form even larger communications networks. However, bridging and routing increase the processing load on machines that interconnect the various physical networks.[0003]VLANs have been developed to address various deficiencies in bridged and routed networks and to allow LANs to be bridged in virtually any desired manner, independently of physical topology of the networks. VLANs...

AI Technical Summary

Benefits of technology

[0007]If the VLAN tag associated with the received layer 2 frame is a translation VLAN tag, copies of the layer 2 frame may then be created and flooded to member VLANs and to ports of the translation VLAN other than the source port. Each copy of the layer 2 frame may include a different VLAN tag than the input layer 2 frame. The different VLAN tags in the frame copies sent to the member VLANs may be associated with each member VLAN. By maintaining associations between VLANs and performing the VLAN translations, the layer 2 switch expands the broadcast and flooding domains of translation and member VLANs, while maintaining isolation between the traffic of member VLANs.

[0009]In one implementation, a layer 2 switch includes a layer 2 forwarding table and an output tag table. The forwarding table includes entries that are indexed by a combination of destination MAC address and VLAN tag. The result of locating a matching entry in the forwarding table is an index to the output tag table. The output tag table includes replacement VLAN tags for outgoing frames. Multiple entries in the output tag table may be accessed in response to one lookup in the forwarding table when multiple copies of a received frame are being sent to different VLANs. Because the output tag table maintains multiple VLAN associations for a single input VLAN, efficient VLAN translations can be achieved.

Problems solved by technology

However, bridging and routing increase the processing load on machines that interconnect the various physical networks.

One problem with using VLAN tag stacking is that tag stacking only provides a mechanism for switching frames in the interconnecting network.

Another problem with tag stacking is that it increases the complexity in decoding frames in the interconnecting network.

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